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21 cm to Inches

21 centimeters equals 8.2677 inches — about 8 1/4″ on a tape measure.

Conversion factor
1 cm = 0.393700787402 in
Millimeters
210 mm
21 cm =8.2677 in8.2677 inches

Show the work

  1. in = cm × 0.393700787402
  2. 21 × 0.393700787402 = 8.2677 in
  3. Equivalently, because 1 in is exactly 2.54 cm: 21 ÷ 2.54 = 8.2677 in
Centimeter to inch conversion table
cminft & in
10.39370.4 in
20.78740.8 in
31.18111.2 in
41.57481.6 in
51.96852 in
103.9373.9 in
155.90555.9 in
207.8747.9 in
259.84259.8 in
3011.81111.8 in
4015.7481 ft 3.7 in
5019.6851 ft 7.7 in
6023.6221 ft 11.6 in
7027.55912 ft 3.6 in
7529.52762 ft 5.5 in
8031.49612 ft 7.5 in
9035.43312 ft 11.4 in
10039.37013 ft 3.4 in
12047.24413 ft 11.2 in
14055.11814 ft 7.1 in
15059.05514 ft 11.1 in
15561.02365 ft 1 in
16062.99215 ft 3 in
16564.96065 ft 5 in
17066.92915 ft 6.9 in
17568.89765 ft 8.9 in
18070.86615 ft 10.9 in
18572.83466 ft 0.8 in
19074.80316 ft 2.8 in
19576.77176 ft 4.8 in
20078.74026 ft 6.7 in

21 cm at a glance

Inches
8.2677 in
Nearest 1/16 in
8 1/4 in
Nearest 1/8 in
8 1/4 in
Feet & inches
8.27 in (under 1 ft)
Millimeters
210 mm
Meters
0.21 m

How to convert 21 cm to inches

inches = cm ÷ 2.54
21 ÷ 2.54 = 8.267717 in

The inch has been defined as exactly 2.54 cm since 1959, so dividing by 2.54 is exact; the long decimal is just what that division produces. Multiplying by 0.3937 gives the same answer to four places.

Quick estimate

Multiply by 4 and divide by 10: 21 × 0.4 = 8.4 in. That overshoots by 0.13 in (about 1.6%) — fine for a rough check.

Reading 21 cm on an inch tape measure

US rulers mark fractions of an inch rather than decimals. Here is 8.2677 in rounded to each common mark, with the error that rounding introduces:

PrecisionTape-measure readingError
1/2 in8 1/2 in+5.90 mm
1/4 in8 1/4 in−0.45 mm
1/8 in8 1/4 in−0.45 mm
1/16 in8 1/4 in−0.45 mm
1/32 in8 9/32 in+0.34 mm
21 cm = 8.27 in051015200123456789cmin
21 cm = 8.27 in on a dual-scale ruler: centimeters along the top edge, inches along the bottom.

Things about 21 cm long

  • About the same as the short side of an A4 sheet, 21 cm (8.27 in).
  • About the same as the short side of US letter paper, 21.59 cm (8.5 in).
  • 10% longer than a new, unsharpened pencil (about 7½ in), 19.05 cm (7.5 in).
  • Paper and screens. 21 cm is 8.27 in — 0.23 in less than the width of US letter paper.
  • Carry-on bags. Most US airlines limit carry-ons to 22 × 14 × 9 in, about 56 × 36 × 23 cm, so 21 cm fits even the shortest side.

Centimeters near 21 cm

CentimetersInchesNearest 1/16 in
16 cm6.2992 in6 5/16 in
17 cm6.6929 in6 11/16 in
18 cm7.0866 in7 1/16 in
19 cm7.4803 in7 1/2 in
20 cm7.874 in7 7/8 in
21 cm8.2677 in8 1/4 in
22 cm8.6614 in8 11/16 in
23 cm9.0551 in9 1/16 in
24 cm9.4488 in9 7/16 in
25 cm9.8425 in9 13/16 in
26 cm10.2362 in10 1/4 in

Going the other way: 8 inches to cm is exactly 20.32 cm.

Frequently asked questions

How many inches is 21 cm?

21 cm is 8.27 inches (8.2677 to four places), found by dividing 21 by 2.54.

What is 21 cm in inches as a fraction?

To the nearest sixteenth, 21 cm is 8 1/4 in; to the nearest eighth it is 8 1/4 in.

Is 21 cm bigger than an inch?

Yes. 21 cm is 8.27 in, because one inch is only 2.54 cm.

How do I convert 21 cm to inches without a calculator?

Multiply by 0.4 for a quick estimate (8.4 in), then shave off about 1.6% to get close to the exact 8.27 in.

Need a different value? Use the CM to inches converter, or browse the CM to inches chart.